The present invention is in the field of display apparatus having capability of displaying alpha-numeric characters as selected by the electrical activation of one or more of a plurality of light emitting diodes (hereinafter "LED"). Visual displays and the manner and means for selectivity of the display are known in the prior art. Representative of the prior art is Jankowski et al. U.S. Pat. No. 3,786,499 which describes a package for selectively displaying characters, as above, whereby light from an LED or a plurality thereof each of which defines a point light source may be perceived at a viewing plane at the end of a light pipe whose outline at the plane may be segmentary or of any particular shape as determined by the character to be displayed. The particulars of the apparatus briefly described and more particularly described in the Jankowski et al. patent as well as others similar thereto are well known in the prior art.
The present invention is an improvement over the structure such as disclosed by Jankowski et al. Particularly, the present invention is directed to an improvement in the manner of electrical connection of each LED in an electric circuit whereby it may be selectively energized for reasons as have been pointed out. In Jankowski et al. each LED is indicated as being connected by a first electrical connection as by soldering to the substrate upon which it is supported while the other electrical connection is provided by a wire at the top surface of each LED which is connected to a conductive post. The conductive post is the common terminal. It has been found that one of the most fragile points of an LED for use in a display is the wire bonding of the base chip to a conductor and its connection to the common terminal. To this end the wire may be of a diameter of about 0.001 inch and as such, it requires the exercise of extreme care in the technique, such as soldering or the equivalent, so that the LED may be connected into a circuit whereby it may be energized. The criticality of this operation introduces production costs and the fragility of the connection is a source of problems throughout the life of the display apparatus. Thus, improper handling, excessive vibration or shock or a host of other occurrences may cause the connection either to break loose from the post to which it is connected or break loose from the LED itself.